Process and apparatus for cracking hydrocarbons



Jan. 19, 1932. N, E QOMls Ef AL' 1,842,104

PROCESS AND APPARATUS FOR CRACKING HYDROC'ARBONS 4Filed July 22. 1925 2 Sheets-Sheet l NHSNN RSN@ N953 Ps Aw-ANELELOOWS NeRLaRMAQHAm noanto'cs Jan'. 19, 1932. N. E.- LooMls r-:T AL 1,842,104

PROCESS AND APPARATUS FOR CRACKING HYDROCARBONS Filed July 722, 1925 2 ShetS-Sheet 2 /r/aZ Patented Jan. 19, 1932 UNITED STATESy EATEANIEL E Looms Ami MERLE n.

PATENT a oFF-ica menen, or ELIZABETH, NEEJEESEY, As-

SIGNOR-S T0 STANDARD OIL DEVELOPMENT COMPANY, A ('JORIEOEtAI'IOlSI'` OF DELA- WARE PROCESS .AlN'D APPARATUS FOR CRACXIG HYDBOCABBONS I Application led. July 22,

This invention relates to improvements in processes and apparatus for the cracking of hydrocarbons into lower boilingproducts., The invention will be fully understood from the following description, taken linconnection with the accompanying drawings, in which Fig. 1 is a diagrammatic elevation of one suitable form of apparatus; and

Fig. ,2 is a partial plan'view of the same, showing the arrangement' of the digesting chambers or soaking drums.

In the` present invention a very fiexible system is provided, by means of which stocks of varying grades may be treated under the conditions best suited for high yields of low boiling products from each stock. The ap paratus will first be described and then its utilization will be particularly pointed out in connection with the treatment of typical feed stocks. y

Referring to the'drawings, reference numeral 1 denotes a shell still or equivalent distillation or vapor-separating means, arranged in aV furnace setting 2. The still 1 is preferably provided with internal horizontal ues 3, through which hot combustion gases from the furnace pass to astack 3. The still is connected throughline 4 with condensing and' fractionating equipment, such as a bubble tower 5. This tower has the usual plates 6, receiving pan 7, vapor heat exchanger 8, vapor line 9, and condenser 10. The lower portion of the tower constitutes a chamber 5 for accumulation of residuum andcondensate, and for other purposes.

A condensate draw-off line 11, having a valve 12, leads from the'pan 7 toy the still 1. A line 11a, leading to storage, the cracking coil, or other suitable equipment,A is also connected with line 11. A line 11b is provided for the purpose of passing the condensate to the cracking coil.l Valves 11 and 11" control the ow through these lines. Another draw-off line 13 is arranged to receive oil from the bottom of the tower 5 and convey it through branch line 14 to the pump or pumps 15 which forward the oil through line 15y to the cracking coil 16' and .ligesyti-ng chamand branch 1925. serial 1ro. 45,194. i

connected to line 13 and pipes (not shown) may convey the oil from the accumulator to pumps 15. A

Alternatively, the oil from the'bottom of tower5 may be drawn olf through line 13 pi e 19 to a cooler (not shown) or other suita le means. A valve 20 is installed in line 13 between the branches 14 and 19. A by-pass 21, -having a Ivalve 22, connects branch line 14 with the outlet pipe 23 from the bottom of the still 1. A 'valve 22 is installed in line 23 and a valve 22" in line 14 below the by-pass 21. Line 23 discharges liquid oil from the still through the by-pass 23a into a tar heat exchanger .24, or directly into line 14, inaccordance with the regulation of valves 22 and 23. A line. 25 .serves for the withdrawal of tar from the exchanger 24, and this line preferably connects with line 19.

The feed stock for the system passes from the storage tank 26 through line 27 to the accumulator tank 28 and thence throu h line v33 into the lower portion of the still 1. Al-

ternatively, the oil may by-pass the tar heat exchanger .by being diverted to branch line 34 in which a valve 34 is installed. It will be seen that feed stock free kfrom condensate is introduced into a distillation zone. This is important especially in those cases where it is desirable to keep some or all of the condensate from passing tothe cracking zone, for the avoidance of carbon troubles and the like.

The digesting chambers or soaking drums 17, 18l discharge through*` the line 35 and pressure release `valve 36 into the line 37. Valves 38 and 39 are interposed respectively on opposite sides of the inlet to line 37. By proper actuation of these valvesthe oil may be sent either into the still through branch line 33 100 or into the bottom of the tower 5 through the main line 37.

The cracking coil 16 may discharge into either or both of the drums 17, 18. These are preferably arranged in parallel, as shown, and are connected with the line from the cracking coil by branch pipes 40, 41 in which valves 42 and 43 are respectively arranged. Branch lines 44 and 45 connect the drums with line 35.

The coil`and drums are designed to be operated at relatively high pressure, as is iwell understood in the art, and the drums should be thermally insulated. as by means of a lagglng 46, or

exchanger 24, 'and is then passed continuously into the still 1 through lines 32 and 33 at a temperature around 500 F. The preheated oil becomes mixed with the cracked stock entering the still from the digesting chambers or soaking drums 17, 18 through lines 35, 37 and 33. Distillation takes place in the still 1 and vapors pass up into the tower 5 for fractionation. Additional heat v may be supplied to the still as .described below. The-bottom of the tower may serve as a hot accumulator for the condensate stock which is to be recycled through the system, or the accumulator 13a may be used. This stock is drawn ott' through lines 13 and 14 and is passed by the pumps 15 through line 15 to the cracking system. Valves 12, 20, 22, 23', 34', and 38 are closed and valves 22', 22, 31', and 39 are open during this operation. One or both of valves 42 and 43 are open in accordance with whether one or both drums are in use.

The temperature at which oil enters the drum or dru-ms may be about 850 F. vThe temperature of the product Withdrawn from the drum or drums may be about 775 F. Vapors and liquids together are passed into the still through lines 35, 37 and 33.

The pressure in the coil and drums may be about 300 to 350 lbs. per sq. in. This pressure may beA reduced through the release valve 36 to substantially atmospheric pressure. The cooling incident to expansion of vapors may reduce the temperature of the oil beyond the release valve to ahoutA725 F.

Thel heat content of this oil is not usually suffielent to distill the crude'oil. The proper amount of additional heat is therefore supplied .to the still, preferably by passing ht Y drums.

combustion gases through its internal lues 3. This method of heating is preferred, as it in large measure avoids the coking difiiculties in the still which might be encountered if it were attempted to apply external heat. However, some external heat may be applied to the still in the installation shown. All the heat may be supplied externally, if adequate precautions are taken to prevent overheating, for example by using muflle furnaces.

The temperature of the oil in the still may be about 650 F. The still may be operated under pressure, for example lbs. per sq. in. In treating crudes such as Smackover crude. however, the primary purpose of the still is to strip the feed stockand the distillation ordinarily best conducted under atmospheric or lower pressure so that the heat requn'cments may be kept low. Pressure in the still is more desirable when gas oil or the like is being cracked, as will be referred to later.

In starting the operation the still 1 is charged with the feed oil and tired to a distillation temperature. Meanwhile., gas oil or the like is supplied from an external source to the cracking coil, whichlis suitably fired. The eiiluent from the coil is discharged into the drum or drums and the cracked product is delivered into the still in the manner dw scribed. As soon as the system produces au adequate amount of gas oil, this alone is used as the stock to be cracked. It is collected in the bottom of tower 5 and passes through lines 13, 14, and 15 to the cracking coil.

The cracking coil and soaking' drums may be operated under any suitable conditions. Generally, the oil will be passed through the coil at such a velocity that most of any car# bon forming therein is swept out into the Conversion takes place in the coil and drums in a manner well understood in the art; that is, incipient or partial couvern sion occurs in the coil and further conversion is effected in the drum, by virtue of the contained heat of the oil.

It will be noted that the crude oil itself does not enter the cracking apparatus in this embodiment of the invention. Only the distillate from the crude is cracked. In this way scaling and coking troubles are substantially avoided. The still and tower act as a dehydrating plant, thus obviating the need for supplying separate equipment for this purpose.

When operating with feed stock that does not tend to deposit so much carbonaceous matter, such asPamlco crude, in which it is necessary or desirable to crack the crude, the following procedure is adopted: The feed stock is preheated as before by passing through the vapor heat exchanger and the tar heat exchanger andis passed into the still. Heat is suitably applied to the still to distill the feed oil. Vapors are taken oi into the tower Y .the residual oil is drawn from the still through lines 23 and 14 and is conveyed by pump through line 15' to the cracking coil.

The cracked product is passed from the drums into the base of the tower 5 lthrough lines and 37. `The residuum and condensate collecting in the bottom of tower 5' is drawn off through lines 13, 14, and 21 to the tar heat exchanger, through which it passes inheat interchanging relation with the feed stock entering the system. In running Panuco crude or the like, valves 12, 20, 22', 22", 34', and 39 are closed and valves 22, 23', 31', and 38 are open. An intermediate fraction may be taken oif from an 7 by opening valves 12 and 11" and closlng valve 11'. Ordinarily the pan will be allowed to overflow and all condensate will be taken off from 'the bottom of 'the tower. The still may be operated under pressure, as described above.

It will bey noted that the principal difference between this operation and that described for Smackover crude is that the re? siduum from the feed oil is cracked and'that the cracked. product is passedinto the tower withdrawn through lines 11 and 11a to storhot stock.

instead of intothe still.

Also, the heating fluid supplied to thevtar heat exchanger 24 is the hot heavy residuum and condensate tending to accumulate in the bottom of tower 5. This material supplies an amount ofheat comparable to that derived from still residuum in the lSmackover process :described above. v

When operating with gas oil or the like,

lthe following procedure is preferred: Gas o1l is brought in'through the vapor heat exchanger 8 and lines 31, 34, 32, and 33 into the still. There is very llittle residuum formed when gas oil is thestock being treated, -and for this reason the tarp heat exchanger is not ordinarily used. The still is preferably operated under pressure, for example 6() lbs. per sq. in. asin ,this way a higher preheat of the gas oil is possible than when working at normal pressure. An additional advantage of pressure-isthat it permits a forced feed to the pumps 15, thereby prevent ing possible loss of suction when pumping ed in the pan 7 for return to the still through line 11. If desired, this condensate may be age orpassage to the crackin coil'. The cracked product from the soaking drums is injected into the tower, as described in connection `Vwith the Panuco operation. The heavy residuum with perhaps a small portion f of condensate is taken off from the bottom the tar heat exchanger and utilized to heat the gas oil, if it is desired to secure additional preheat. In this operation (the tar heat exchanger not ibeing used Yand condensate being returned) valves 1l", 22, 22',l 22", 31', and, 39 are closed and valves 11', 12, 20, 23', 34', and 38 are open.

While the useof digesting drums is preferred, it will be understood that the invention is not limited to any particular equipment for cracking. Various modifications and alternative arrangements may be made within the scope of the appended claims, in which it is our intention to claim all novelty inherent in the invention as broadly as the prior art permits.

'We claim:

oil to a distillation temperature in a distillation zone,'fr actionating vapors therefrom in a fractionating zone and recovering the distillate, supplying to the distillation zone feed Y oil unmixed with condensate formed in said fractionatingzone, cracking the unvaporized fresh feed oil that hasbeen ysubjected to' distillation,'and injecting the hot cracked vaporous and liquid product into the fractionation zone.

2. Process of cracking hydrocarbon oil, comprising subjecting lthe oil -to a distillation mi.V

temperature, fractionatingvapors therefrom i in a fractionating zone and recovering the distillate, supplying to the distillation zone feed oil free from condensate formed 1n sald fractionation, heating the oil that has beensubjected to distillation to a cracking teinperature to produce partial cracking therein, digesting the partially cracked oil,.and 1njecting the same into the fractionatlon zone.

3.l Processl of cracking. h'drocarbon 0 11, comprising'supplying fresh eed oil to a .distillation zone in which it is heated to a distillation temperature, fractionating vapors therefrom in a fractionating zone to produce a distillate product, withdrawing and cracking hot' residuum` from the distillation zone, delivering the hot cracked product into the base of the fractionating zone, and separately withdrawing liquid residuum and partial condensate from the fractionating zone.

4. Apparatus for cracking hydrocarbon oil, comprising cracking equipment, aj st1ll,

. means for heating the same. means .for sup- 1-20' plying'feed -oil -to the still, fractionation apparatus connected tothe still, means for taking off a light distillate and an intermediatel fraction from the fractionationV apparatus,

a chamber in the lower portion of theffrac-` tionaton apparatus, means for passing oil from the still to the cracking equipment, and

means vfor delivering .products 'from thecracking equipment either to said still or said chamber.

5. .Apparatus for Q cracking 'hydrocarbonoil, comprising cracking equipment, a still, means for heating the saine, means :tor supplyingl feed oil to the still, fractionation apparatus connected to the still, means for taking oil' a light distillate and an intermediate fraction from the fractionation apparatus,

means for delivering products from the cracking equi purent either to said still or said. fractionating apparatus, means for withdrawingl liquid from the fractionating apparatus,'1neans for returning the intermediate fraction to the still, and means for supplying to the cracking equipment either said intermediate fraction or feed oil from the still. i

G. Apparatus according to claim 5, comprising a heatexchanger, moans for passing feed oil therethrough, and means for passing, in heat interchange with such oil, either lliquid oil from said chamber or from said still.

7. Process of cracking hydrocarbon oil, comprisingl supplying the oil to a distillation Zone in which it is heated toa distillation temperature,l fractionating vapors therefrom in a fractionating zone to produce a distillate product, withdrawing and heating the hot residuum from the distillation zone to a cracking temperature to partially crack the same, digesting the hot partially cracked stock to produce further cracking therein, delivering the hot digested product into the lower portion of the fractionating zone, and separately withdrawing liquid residuum and partial condensate from the fractionating zone.

8. Process of cracking hydrocarbon oil, comprising supplying the oil to a distillation zone in which it is heated to a distillation temperature, fractionating vapors therefrom in a fractionating zone to produce a partial condensate and a distillate product, returning such partial condensate to the distillation zone, withdrawing and cracking the hot mixture of residuum Jfrom the oil supplied to the distillation zone and the partial condensate,

passing the hot cracked product to the frac- Y tionating zone, and withdrawing liquid residuum from the .fractionating zone.

9. Process according to claim 8 in which the withdrawn hot mixture of residuum from the oil supplied to the distillation zone and the partial condensate is rst subjected to incipient cracking and then to a digesting operation.

NATHANIEL E. LOOMIS. MERLE R. MEACHAM. 

